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- Guenard, Guillaume, et al.
(author)
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Comparison between activity estimates obtained using bioenergetic and behavioural analyses
- 2008
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In: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 65:8, s. 1705-1720
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Journal article (peer-reviewed)abstract
- Activity rate of Arctic char (Salvelinus alpinus) held in 90 m2 littoral enclosures were estimated using bioenergetic (with consumption estimated using stable caesium, 133Cs) and behavioural approaches (with fish movements quantified using video cameras). We found no statistically significant difference between values of activity rate obtained using the two approaches for three of the six experiments we performed. However, there was no relationship between estimates of activity rate obtained using the two approaches. Discrepancies may arise from the difficulty to meet assumptions regarding the temporal stability of the concentration of 133Cs in fish diet and of the assimilation coefficient of this tracer. When fish remain in an area where their behaviour can be well described (e.g., enclosure, habitat patches of littoral zones, coral reefs), the behavioural approach appears more robust to estimate activity rate because it depends most on a variable that is easiest to estimate (the number of movements performed). When these conditions are not met (low fish densities or major fish migrations), a reliable assessment of the concentration and assimilation of 133Cs in stomach contents appears critical to implement the bioenergetic approach based on this tracer.
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| 2. |
- Guenard, Guillaume, et al.
(author)
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Experimental assessment of the bioenergetic and behavioural differences between two morphologically distinct populations of Arctic char (Salvelinus alpinus)
- 2010
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In: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 67, s. 580-595
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Journal article (peer-reviewed)abstract
- A common environment experiment was conducted to assess the magnitude of the difference in growth, consumption,activity rate, and spatial and temporal patterns of habitat use between morphologically different populations ofArctic char (Salvelinus alpinus) originating from two Norwegian lakes. These two lakes contrasted sharply in terms of surfacearea, depth, elevation, length of the winter period, and fish community structure (presence–absence of brown trout,Salmo trutta). The experimental framework encompassed four littoral enclosures (average volume, 146 m3) stocked withchar from either of the two populations with duplicated treatments. Char morphology was quantified with numerical imageanalysis, food consumption was estimated using caesium analysis (133Cs), and activity cost and patterns were determinedusing video cameras. Char populations were morphologically distinct and reacted differently in growth (1.9-fold differencebetween populations), food consumption (3-fold difference), and spatial activity patterns (20-fold difference) to the conditions prevailing in the enclosures. The results highlight that functional differences between morphologically distinct charmay drive important differences in their bioenergetic and behavioural responses when exposed to similar environmentalconditions. Such functional differences should be incorporated when developing habitat or trophic cascade models.
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| 3. |
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| 4. |
- Jonsson, Bror, et al.
(author)
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Production of juvenile salmonids in small Norwegian streams is affected by agricultural land use
- 2011
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In: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 56, s. 2529-2542
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Journal article (peer-reviewed)abstract
- 1. We estimated the biomass and production of juvenile anadromous brown trout (Salmotrutta) and Atlantic salmon (Salmo salar) (parr) in 12 streams in the Skagerrak area ofNorway to identify controlling environmental factors, such as land-use and waterchemistry.2. Production estimates correlated positively with fish density in early summer, but notwith the size of the catchment. The summer biomass of age-0 brown trout and Atlanticsalmon was smaller than that of age-1 and constituted 27.4 and 25.7%, respectively, of thetotal biomass of the two groups.3. Mean production of brown trout from July to September varied between streams, but inmost cases it was below 2 g 100 m)2 day)1. Yearly cohort production from age-0 in July toage-1 in July was 10 g m)2 or less, with mean annual production of 1.32 g 100 m)2 day)1,equivalent to 4.8 g m)2 year)1. The corresponding annual cohort production of Atlanticsalmon was 0.38 g 100 m)2 day)1 or 1.4 g m)2 year)1. Annual production to biomass ratio(P⁄B) for brown trout of the same cohort in the various streams was between 1.47 and 4.37;the overall mean (±SD) for all streams was 2.25 ± 0.94. Mean turnover rate of Atlanticsalmon was 2.73 ± 0.24.4. Production of 0+ brown trout during the summer correlated significantly with thepercentage of agricultural land and forest⁄bogs in the catchment, with maxima at 20 and75%, respectively. Age-0 brown trout production also correlated with concentration ofnitrogen and calcium in the water, with maxima at 2.4 and 14 mg L)1, respectively.5. The results support the hypothesis that brown trout parr production reflects the qualityof their habitat, as indicated by the dome-shaped relationship between percentage ofagricultural land and the concentration of nitrogen and calcium in the water.
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